Longannet power station
|Longannet power station|
Longannet power station in 2014
|Operator(s)||South of Scotland Electricity Board
|Annual generation||9,525 GWh (2012)|
|grid reference NS953852|
Longannet power station // is a large coal-fired power station in Fife capable of co-firing biomass, natural gas and sludge. The station is situated on the north bank of the Firth of Forth, near Kincardine on Forth. Its generating capacity of 2,400 megawatts is the highest of any power station in Scotland. The station began generating electricity in 1970, and when it became fully operational it was the largest coal-fired station in Europe. It is now the third largest, after Bełchatów in Poland and Drax in England, and the 21st most polluting.
The station was opened in 1973 and operated by the South of Scotland Electricity Board until 1990 when its operation was handed over to Scottish Power following privatisation. The station is a regional landmark, dominating the Forth skyline with its 183 m (600 ft) chimney stack. Longannet lacks cooling towers, instead using water from the River Forth for cooling.
The station was designed by Scottish architects Robert Matthew, Johnson Marshall & Partners. Construction began in the mid-1960s, 4 km (2.5 mi) downstream of the existing Kincardine power station. The station was constructed on 30 hectares (74 acres) of land reclaimed from the Firth of Forth using ash from the Kincardine station. It began generating electricity in 1970, with a design lifetime of 30 years, and was in full operation by 1973. At the time of its completion, the station was the largest in Europe.
The facility was operated by the South of Scotland Electricity Board until 1990 when the electricity industry in the UK was privatised. Since then it has been operated by Scottish Power, a subsidiary of Iberdrola.
The station is expected to close by 2020. The plant is currently opted in to the UK Transitional National Plan, placing limits on its sulphur dioxide, nitrous oxides and particulates emissions in the period to 2020. The plant is testing additional technologies that could permit it to operate beyond 2020 under the EU Industrial Emissions Directive.
Design and specification
Longannet has an installed capacity of 2400 MW and a declared net capacity of 2304 MW due to operational losses. The station produced 9,525 GWh of electricity in 2012, an increase on the 9,139 GWh produced in 2011.
The station consumes up to 4,500,000 tonnes (4,400,000 long tons; 5,000,000 short tons) of coal each year. Coal is delivered either by road or rail to the station's coal store, which has the capacity to hold up to 2,000,000 tonnes. It is then fed from the coal store to the boiler house by a conveyor belt capable of carrying 3500 tonnes of coal per hour.
Each of the four boilers is serviced by eight pulverising units each capable of processing 40 tonnes of coal an hour. The front-wall-fired Foster Wheeler boilers can each burn around 250 tonnes of coal an hour at full load. There are two forced draft and two induced draft fans on each boiler. Each boiler provides around 1800 tonnes per hour of steam at a pressure of 168 bars (16,800 kPa) and a temperature of 568 °C (1,054 °F) to two 300 MW General Electric Company turbo generators. The thermal efficiency of the plant is around 37%.
Coal was originally supplied directly by conveyor belt from the neighbouring Longannet Colliery, until it closed in 2002 after a flood. Around half of the coal used is Scottish, and the rest must be imported, the majority via the former British Steel ore loading facility at Hunterston Terminal in Ayrshire. Onward transport is by rail and the level of traffic required to supply Longannet's fuel demand caused congestion on the Scottish rail network. An alternative route, the Stirling-Alloa-Kincardine rail link, at the mouth of the river Forth was reopened in 2008, and is also used to deliver coal.
The chimney is 183 metres (600 ft) tall, but the station does not have cooling towers, instead using water drawn from the Firth of Forth at a rate of 327,000 cubic metres (11,500,000 cu ft) per hour for the station's cooling condensers. The water is passed through coarse screens and then circulated by four electrically driven pumps. Once circulated through the station's condensers, the water is discharged into a mile long cooling channel, where heat is dissipated before the water reaches a wide part of the Forth. Water used by the boilers is on a different cycle, and must be deionised. Losses from this supply are made up by a plant capable of treating 218 cubic metres (7,700 cu ft) of water per hour.
Electrostatic precipitators and sulfur trioxide conditioning
The station is fitted with electrostatic precipitators (ESP) to reduce the stations particulate emissions. In the late 1980s the station's units were fitted with sulfur trioxide (SO3) conditioning equipment to lower the fly ash's electrical resistivity. This was to ensure the station maintained allowable particulate emissions. Between 1989 and 1994 the station's ESPs were given a major refurbishment. This meant that the SO3 conditioning equipment did not need to be operated as frequently to maintain the allowed level of particulate emissions. This is beneficial as SO3 is hazardous.
In 1994, the station was awarded funding from the European Commission under the THERMIE Demonstration Programme. With this money, Unit 2 at the station was retrofitted with Gas-reburn Technology. This is the largest scale application of this technology in the world. In this process, natural gas is injected into the boiler. This cuts NOx emissions from Unit 2 by 50%, as well as giving a reduction in CO2 and SO2 emissions. Also in 1996, all of the station's boilers were fitted with Low NOx burners. This reduced the station's NOx emissions by 40%.
The blend of coal fed to each unit is intended to minimize emissions of sulphur.
Carbon capture and storage
The UK's first ever carbon capture and storage (CCS) unit was commissioned at the station in 2009. It closed in 2011 after it became clear that it was not financially viable. Plans for a UK Government funded project to convert Longannet to CCS were abandoned in 2011 and no further plans for CCS at Longannet have been announced.
Environmental and health impact
In 2003, Longannet was named as Scotland's biggest polluter in a report by the Scottish Environment Protection Agency (SEPA). The station produces up to 4,350 tonnes of ash per day. This is piped to ash lagoons on the nearby Preston Island, where it is stored in former salt pans. This is then landscaped and used to reclaim the land from the Firth of Forth.
To improve environmental emissions, Longannet is now fitted with 'Low-NOx' burners to limit the formation of oxides of nitrogen and a 'Gas Reburn system' that uses natural gas to convert NOx into nitrogen and water vapour. Longannet used to burn up to 65,000 tonnes of treated and dried sewage sludge per year, which has a similar calorific value to low-quality brown coal. In 2005, a judge ruled the burning of sludge as illegal, but the SEPA continued to allow Scottish Power to burn the sludge illegally as part of an agreement which originally required Scottish Power to construct, and have in operation, a biomass plant in 2010. All burning of biomass at Longannet - including waste-derived fuel and sawdust pellets - ceased in April 2012.
In 2007, the WWF named Europe's 30 most climate polluting power stations in absolute terms; of these, Longannet was the most polluting in the UK (relative to power output). It is the 21st most polluting power station in Europe.
According to a Greenpeace-commissioned report by Stuttgart University on the health impacts of the biggest coal-burning power plants in Europe, Longannet was held responsible for 4,210 lost 'life years' in 2010.
|Wikimedia Commons has media related to Longannet Power Station.|
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